David GlanzmanWe are interested in the cell biology of learning and memory in simple organisms. We use two animals in our research, the marine snail Aplysia californica, and the zebrafish (Danio rerio). Work on Aplysia: This invertebrate has a comparatively simple nervous system (~ 20,000 neurons) that provides a valuable model system for neurobiological investigations of simple forms of learning, including habituation, sensitization, and classical conditioning. Another advantage of Aplysia is that neurons known to mediate specific behaviors in the animal can be placed into dissociated cell culture where they will reform their synaptic connections. These in vitro synapses are extremely useful for cellular and molecular analyses of long-term memory. Currently, my laboratory is attempting to understand how long-term memories persist. We have found that an isoform of protein kinase C, known as PKM, appears to play a key role in the maintenance of long-term sensitization in Aplysia. Work on the zebrafish: The zebrafish is a popular organism for molecular and genetic studies of development. However, it has significant advantages for cell biological analyses of behavior, including learning and memory. The zebrafish is amenable to both forwards and reverse genetics. Furthermore, although it is a vertebrate with a complex vertebrate nervous system, it possesses reflexive behaviors that are mediated by relatively simple neural circuits in the spinal cord and brainstem. Finally, zebrafish larvae are transparent, which facilitates the use of imaging techniques to study learning-related neural activity in the intact animal. We are interested in the neural basis of nonassociative and associative modification of the zebrafish’s startle reflex. At present we are using electrophysiological, genetic, and imaging techniques to analyze the mechanisms of habituation and sensitization of the startle reflex. In the future we hope to examine classical conditioning of this reflex.